Automobiles generally include three basic components for creating motive force: an engine, a powertrain, and wheels. The powertrain transmits torque generated by the engine, typically through either a manual or automatic transmission, to the wheels, thereby providing movement of the vehicle. In general, automatic transmissions include a torque converter that transfers engine torque from the engine crankshaft to the transmission input shaft. The transmission input shaft couples to one or more planetary gear sets, through frictional elements or clutch assemblies, to provide various amounts of torque to the transmission output shaft. The transmission output shaft typically powers a differential that drives the wheels.
Automatic transmissions generally use a fluid control assembly, which includes valves, accumulators, and a fluid pump, to engage the frictional elements and thereby transition from one gear to the next. In general, the fluid pressure must be carefully managed such that sufficient fluid line pressure is provided to engage and prevent slip between the frictional elements. If insufficient line pressure is provided, the frictional elements do not fully engage and slip occurs resulting in power loss and damage to the transmission. On the other hand, if excessive line pressure exists, the fluid pump torque may be higher than necessary, thereby resulting in poor fuel efficiency.
In some instances, however, it may be desirous to provide a different fluid pressure than that specified in the original equipment manufacturer (OEM) set-up. The shift “feel” or “firmness” of shifting between gears is largely dictated by the pressure of the fluid in the transmission. For example, if the fluid is provided at a higher pressure the result is a “firm” or hard shift between gears, while fluid at a lower pressure will produce a “softer” shift. In many types of transmissions, the ability to increase or decrease the fluid pressure is as simple as replacing a spring or a valve in the fluid control assembly. However, for some transmission systems, known as “closed loop” systems, an integrated controller will automatically correct the pressure to a predetermined value if one of the aforementioned techniques is employed. Thus, for some automotive enthusiasts, obtaining the perfect shifting feel without damaging transmission components has heretofore been out of reach.